To prevent the deterioration of adhesion between a hard coat film and an antireflection film of a plastic lens and abrasion resistance thereof, it is known to treat the surface of the hard coat film with oxygen radicals, that is, with ozone gas or ozone water. One example of the method of producing such a plastic lens is disclosed in JP-A-2001-141905, in which the surface of a hard coat film of a plastic lens substrate with a hard coat film containing titanium oxide fine particles is treated with ozone gas or dipped into ozone water and then an antireflection film is formed on the treated hard coat film through vapor deposition.
However, when the hard coat film formed on a plastic lens substrate contains metal oxide particles other than titanium oxide particles, such as silicon oxide particles, and when its surface is treated with ozone gas or ozone water according to this prior art method, there is a probability that the adhesion of the hard coat film to the antireflection film that overlies it and also the abrasion resistance of the thus-coated plastic lenses inevitably deteriorate.